The overall objective of this research is to understand how we listen to the sound of our own voice while talking and how we use this information to help control our speech. Humans have sophisticated mechanisms for self-monitoring of this vocal feedback during speech that allow for the detection and compensation for vocal errors. Degradation of this self-monitoring, such as following hearing loss, results in difficulty in acquiring and maintaining normal speech and impairs vocal communication. Recent work in both humans and primates has demonstrated a suppression of neural activity in the auditory cortex during vocalization that may play a role in self-monitoring. The origin and significance of this neural activity is unknown. This proposal focuses on determining the neural mechanism of self-monitoring during vocal production and its role in feedback vocal control, using both human subjects and a vocal primate model, the marmoset monkey. Aim 1 tests the hypothesis that suppressed neurons of the auditory cortex in marmosets exhibit self- monitoring activity, and that this neural activity can drive compensatory vocal control. Auditory cortex neurons are recorded from vocalizing marmosets while altering the frequency content of their vocal feedback to induce vocal compensation. Neural recording is followed by electrical stimulation of the auditory cortex in order to disrupt self-monitoring and resulting feedback compensation. These experiments will demonstrate how vocalization self-monitoring activity in the auditory cortex drives feedback vocal control. Aim 2 tests the hypothesis that frontal cortical areas, particularl pre-motor cortex, are the origin of the neural signals that cause vocal suppression in auditory cortex. Neurons in both frontal and auditory cortex of marmosets are recorded simultaneously and quantitative analyses applied to demonstrate neural connectivity between brain regions during vocal production. These results will demonstrate the neural pathways beyond auditory cortex that contribute to vocal self-monitoring. Aim 3 tests the hypothesis that human auditory cortex is necessary for self-monitoring and feedback vocal control of speech. Auditory cortex activity is recorded using intracranial electrocorticographic activity in patients undergoing neura monitoring for epilepsy surgery. Paralleling the animal experiments, electrical stimulation of cortex is performed during pitch-altered speech feedback to demonstrate the role of auditory cortex in feedback compensation. These experiments will have implications for understanding speech motor control and will allow mechanistic comparisons between human speech and animal vocalization. Such comparisons are critical as we attempt to translate results from animal neurophysiology towards understanding human speech production.